Portable electronic devices typically require one or more regulated voltages so as to operate properly. Non-limiting examples of such portable devices include cellular telephones, personal digital assistants (PDAs), global positioning system (GPS) receivers, and a host of others. Often, a single direct-current (DC) source such as a battery is provided as the only supply of electrical energy for the portable device. Circuits commonly referred to as voltage converters provide for the respective DC voltage requirements of the portable electronic device.
One common voltage converter technique is to draw electrical energy from the DC source by way of pulse width modulation (PWM), the stream of pulses then being filtered to provide a regulated voltage to a load. As the voltage and/or current requirements of the load vary, the duty cycle of the PWM stream is controllably adjusted. Plural voltage converters can operate independently such that numerous regulated DC voltages are derived from a single (i.e., common) energy supply.
However, known PWM techniques rely essentially on rapid on-off switching (or coupling) between the energy source (e.g., battery) and the load or loads to be served. This rapid switching is undesirable from both the standpoint of battery life-cycling, as well as the resulting harmonic signals that must be tolerated or otherwise dealt with by the electronic circuitry of the portable device. Therefore, improved systems and techniques for voltage conversion within portable devices are desirable.